Problem
Business Context
StreamCart, a subscription video platform, saw a drop in weekly upgrade rate after changing its pricing page. A product manager wants to know whether the analyst should treat this as an exploratory analysis or a hypothesis-driven test.
Problem Statement
You are given two possible analysis setups based on the same business issue. One uses a pre-specified hypothesis and one starts by slicing the data into many segments after the fact. Decide which setup is hypothesis-driven, which is exploratory, and quantify why the distinction matters statistically.
Given Data
| Scenario | Comparison | Sample Size per Group | Upgrade Rate Before | Upgrade Rate After | Number of Segments/Tests | Significance Level |
|---|---|---|---|---|---|---|
| A | All eligible users, pre-registered before launch | 8,000 | 10.2% | 8.9% | 1 | 0.05 |
| B | Post-hoc search across device country tenure segments | varies | one segment found: 12.4% | 9.1% | 20 | 0.05 |
For Scenario A, assume the observed counts are 816 upgrades before and 712 upgrades after.
Requirements
- Classify Scenario A and Scenario B as exploratory or hypothesis-driven.
- For Scenario A, state the null and alternative hypotheses.
- Conduct a two-proportion z-test for Scenario A.
- Compute a 95% confidence interval for the change in upgrade rate in Scenario A.
- For Scenario B, calculate the family-wise probability of at least one false positive across 20 independent tests at .
- Explain how the statistical evidence should change the analyst's reporting and next step.
Assumptions
- Users in the before and after groups are independent for Scenario A.
- The hypothesis in Scenario A was defined before looking at the results.
- The 20 tests in Scenario B are treated as independent for the false-positive calculation.
- Use a two-sided test for Scenario A.
Practicing as: Data Analyst interview at Siemens HealthineersHi, I'll play your Siemens Healthineers interviewer for the Data Analyst role. Candidates describe these interviews as mostly positive and moderately difficult, so expect me to be friendly and conversational. Take your time with the question above and answer like we're in the room.
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